24
2 Advantages of Hybrid Bioreactor
equations was solved by the method of lines and the entire model was implemented
in a computer program “GMTNCU1.EXE” coded with FORTRAN language [82].
A mechanistic and empirical IFAS model package was developed for predicting
carbonaceous removal and nitrification at steady-state condition for activated sludge
system with integrated sponge media in aerobic zone [83]. The respective computer
program also predicted the amount of sponge media needed for optimizing the design
of IFAS system. The drawback of the model is that it is only applicable for the sponge
media. The said IFAS system consisted of two anaerobic, two anoxic and three aerobic
reactors in series with sponge media installed in aerobic zones running in parallel
with a control system without having any media.
The computer program solved all mass balance equations of both substrate and
biomass simultaneously with a set of non-linear equations using modified Newton–
Raphson techniques. Another drawback of this model was that no biofilm yield and
sloughing rates were considered.
Effort has also been made to develop a simplified mathematical model for
designing the steady-state biofilm activated sludge reactor under limiting substrate
condition [13]. In that model, a simplified expression of J (substrate flux) was used for
avoiding the approximate graphical solution for obtaining J as developed by Suidan
et al. [70]. However, the said model is based on some dimensionless parameters
and it can be analyzed only if the effluent substrate concentration is pre- assigned.
Earlier one activated sludge model (ASM2d) was developed for biological phosphorus removal with simultaneous nitrification–denitrification in the activated sludge
process [64]. The said model was further extended to a steady-state IFAS model by
Boltz et al. [84] using the input taken from biofilm modeling techniques [1]. The said
IFAS model considered competition between the biofilm and suspended biomass
for macronutrients, electron donor and electron acceptor substrates. The theoretical
considerations in the said model include simultaneous diffusion and Monod type
reaction kinetics inside the biofilm. The drawback of this IFAS model is that the
biofilm thickness (L f ) needs to be known as a priori to run the analysis and the fate
of soluble COD is poorly understood.
Eventually, a simplified mathematical model was proposed to provide an accurate
tool for describing the steady-state suspended sludge—biofilm system in the treatment of municipal wastewater [39]. The model was based on a steady-state condition
for biomass and substrate with a rate-limiting substrate concentration in the reactor.
Monod kinetics was used to describe the biomass growth, whereas, the transport
of the dissolved components in the liquid phase was demonstrated by molecular
diffusion as per Fick’s second law.
2 Advantages of Hybrid Bioreactor
equations was solved by the method of lines and the entire model was implemented
in a computer program “GMTNCU1.EXE” coded with FORTRAN language [82].
A mechanistic and empirical IFAS model package was developed for predicting
carbonaceous removal and nitrification at steady-state condition for activated sludge
system with integrated sponge media in aerobic zone [83]. The respective computer
program also predicted the amount of sponge media needed for optimizing the design
of IFAS system. The drawback of the model is that it is only applicable for the sponge
media. The said IFAS system consisted of two anaerobic, two anoxic and three aerobic
reactors in series with sponge media installed in aerobic zones running in parallel
with a control system without having any media.
The computer program solved all mass balance equations of both substrate and
biomass simultaneously with a set of non-linear equations using modified Newton–
Raphson techniques. Another drawback of this model was that no biofilm yield and
sloughing rates were considered.
Effort has also been made to develop a simplified mathematical model for
designing the steady-state biofilm activated sludge reactor under limiting substrate
condition [13]. In that model, a simplified expression of J (substrate flux) was used for
avoiding the approximate graphical solution for obtaining J as developed by Suidan
et al. [70]. However, the said model is based on some dimensionless parameters
and it can be analyzed only if the effluent substrate concentration is pre- assigned.
Earlier one activated sludge model (ASM2d) was developed for biological phosphorus removal with simultaneous nitrification–denitrification in the activated sludge
process [64]. The said model was further extended to a steady-state IFAS model by
Boltz et al. [84] using the input taken from biofilm modeling techniques [1]. The said
IFAS model considered competition between the biofilm and suspended biomass
for macronutrients, electron donor and electron acceptor substrates. The theoretical
considerations in the said model include simultaneous diffusion and Monod type
reaction kinetics inside the biofilm. The drawback of this IFAS model is that the
biofilm thickness (L f ) needs to be known as a priori to run the analysis and the fate
of soluble COD is poorly understood.
Eventually, a simplified mathematical model was proposed to provide an accurate
tool for describing the steady-state suspended sludge—biofilm system in the treatment of municipal wastewater [39]. The model was based on a steady-state condition
for biomass and substrate with a rate-limiting substrate concentration in the reactor.
Monod kinetics was used to describe the biomass growth, whereas, the transport
of the dissolved components in the liquid phase was demonstrated by molecular
diffusion as per Fick’s second law.